Master brake cylinder and switch unit



A. A. BLUEMLE MASTER BRAKE CYLINDER AND SWITCH UNIT April 7, 1942;

Filed March 8, 194C] i l HUH/IH br i far?,

, V@0 lNzN-ro l A ATTORN EY/l Patented Apr. 7, 1942 Arnold A. Bluemle,Anderson, Ind., assigner to General Motors Corporation, Detroit, Mich.,a

corporation of Delaware Application March 8, 1940, Serial No. 322,959

(Cl. G- 52) 2 Claims.

This invention relates to stop light switches for use in automotivevehicle lighting systems in order to indicate to the driver in the carbehind that the brakes in the car ahead are being applied. Heretofore ithas been the practice to use in connection with hydraulic brakingsystems an oilpressure switch for completing the circuit between thecurrent source and the stop light signal mounted on the rear end of theautomobile. As these stoplight switches are relatively expensive and arenot very durable, I have sought to provide an electric switch other thanahydraulic switch whichv I can apply to the braking system in .aneconomical manner. Therefore,v it is an object of the present inventionto provide a switch of simple and economical construction which may becombined with the matter brake cylinder of a hydraulic braking system.

Further objects and advantages of thepresent invention will be apparentfrom the following description, reference being hadto the accompanyingdrawing wherein av preferred embodiment of the present invention isclearly shown.

In the drawing:

Fig. 1 is longitudinal sectional vview of a master brake cylindercombined with an electric switch according to my present invention.

Fig. 2 is a sectional view on ylines 2-2 of Fig. 1.

normal position. The central opening 33 in the washer 21, see Fig. 5,guides the rod 3l.

The exterior upper portion of the casting 2li is provided with a flat orplane surface 35 upon which is mounted the frame or housing 46 of a stoplight switch. Said frame being secured by screws 4I upon the planesurface 35. The housing provides a box-like structure which receives acontact carrier 42 made of Bakelite or other plastic insulatingmaterial. Carrier 42 provides a recess for receiving a contact member 43provided with contact projections 44 for engaging stationary contactmembers 45 which are inserted in a non-conducting cover 46. The inserts45 Aprovide terminal plugs 41 for engaging sockets mounted on the endsof wires, not shown. The cover 46 is held in position by tangs 48provided by the switch case 40 which are deformed into notches 49provided by cover 46." The carrier 42 provides pockets `5l) forreceiving tangs 6I of contact member `43. Carrier 42 drives member 43thru the tangs 5i. A spring` 52 received by pocket in the carrier 42urges the contact buttons 44 against the inner surface of the cover 46.

The carrier 42 is provided on its under side with a notch 55 whichreceives an actuator 56 having a protruding flange 51 engaged by theright-hand end of carrier 42 and having a downwardly turned flange 58extending thru a slot 59 in the bottom of the case 40. Flange 56 carriesa stud 60 which projects thru a notch 6| in washer 21 and engages thepiston member 23. The carrier 42 is urged toward the right by a pair ofsprings 62, Fig. 6, which are received by Fig. 7 is a sectional view online 1-1 of Fig. 6. i

Referring to Fig. 1, 20 designates a casting or housing providing areservoir 2| for receiving hydraulic brake iluid and providing acylinder 22 within which slides a piston 23 provided with rubber orneoprene piston members 24 and 25. The piston 23 is urged toward theleft by spring 26 into engagement with a Washer 21 which is retainedwithin a counterbore 28 ofV part 2|1by wire split ring 29. The normal ornon-braking position of the piston 23 is shown in Fig. 1, there being,

brake uid between piston 25 and an end member or plug 30. To apply thebrakes the piston 23 is'moved toward the right by a rod A3| attached toany suitable brake pedal, not shown. Rod 3i has a head 32 coniinedbetween the piston 23 and the washer 21 when the piston is in thepockets 63 in carrier 42 and which are retained in said pockets by thecover 46. The springs 62 urge vthe carrier 42 against the nange 51 ofplate 56 and consequently urge the stud 60 against the piston 23 againstthe action of spring 26 which. is much stronger than springs 62.Therefore, normally these springs 62 are held in the compressed stateshown in Fig. 6 and the contact buttons 44 are out of engagement withstationary switchcontacts 45. y

lWhen the brakes are applied the piston 23 is Vmoved toward the right bythe pedal operated rod' 3l, from the position shown in Fig. 1. Duringthis movement the switch contact 43 is moved toward the right under theaction of the springs 62 to cause the buttons 44 to engage the contacts45 thereby completing a circuit between a storage battery and'a stoplight. When the pedal operated rod 3| is released, the spring 26 expandsto move the piston 23 toward the left into engagement with the washer21. During this movement of the piston 2l the stud l0 is moved towardthe left thereby moving contact member 43 into the position shown inFigs. 6 and 7 against the action of springs 62 which are very muchweaker than spring 28 which restores the piston 23.

In order that the washer 21 may be in such position that its notch 8|will receive the stud 60 of the switch, said washer is provided with atang 21a received by a notch 28a provided by the casting 2B.

In order to prevent ingress of dirt and water to the master brakecylinder and to protect the connection between the rod 3| and the piston23 and in order to protect the switch, I provide a flexible rubber boot10 having a neck 1I thru which the rod Il extends and having a flangeorA bead 12 which stretched will encompass the casting 20 and theswitch, as shown in Figs. l and 2.

v While the embodiment of the present invention as herein disclosed,constitutes a preferred form, it is to be understood that other formsmight be adopted, all coming within the Scope of the claims whichfollow.

What is claimed is as follows:

i. In a master brake cylinder and stop-light switch unit comprising aplurality of sub-assemblies one of which includes a cylinder memberhaving a notch formed in one end, a piston movable within the cylinder,yieldable means for urging the piston in one direction, and a washerremovably secured to the cylinder member for limiting the movement ofthe piston in one direction, said washer having a. through slot formedtherein and having a projection for registry with the notch to preventthe washer from ton whereby as a result of the movement of the piston inone direction away from its normal position the actuator is effected toclose the switch.

2. In a. master brake cylinder and stop-light switch unit comprising aplurality of sub-assemblies one of which includes a cylinder memb :rhaving a notch formed in one end, a piston mi. vable with in thecylinder, yieldable means for urging the piston in one direction, aheaded rod manually operated for moving the piston in the oppositedirection against `the action of the yieldable means; and a washerloosely assembled with the rod to permit movement of the rod relative tothe washer; means for detachably securing the washer to the cylinderwhereby the movement of the ,rod and piston is limited in said onedirection, said washer having a through slot formed therein and having aprojection for registry with the notch to prevent the washer fromturning relative to the cylinder member;

4and a switch sub-assembly mounted upon the end portion o f -thecylinder, said switch including an actuator movable longitudinally ofthe cylinder and projecting through the slot of the washer and extendinginto the cylinder against the piston whereby as a result of the movementof the piston by the rod theactuator is eiected to close the switch.

ARNOLD A. BLUEMLE.

